Yesterday, I got a co-worker to switch to Ubuntu 8.10 as a primary operating system. The Windows key-Tab for switching between windows had her impressed. We use Sun's VirtualBox to run Windows XP so we can work on Microsoft Visual Studio 2008. The installation went perfectly well as both the partitions were primary partitions.
Today, I convinced another co-worker to use Ubuntu - it was mostly the Compiz Fusion 3D desktop cube that did it for him. Running Sun's VirtualBox for Visual Studio made the deal. However, the installation didn't work - an error was reported at the partitioning phase and apparently, the installer doesn't re-size the extended partition to make room for itself.
Windows is still a part of daily work though... it comes as a part of being in a team developing with the Microsoft .NET Framework 3.5.